UV radiator units for the treatment of gases and especially of liquids like water are widely known. The UV radiation, which is produced by these units, is useful to disinfect water, for example drinking water, which contains bacteria and viruses, and wastewater, which needs to be disinfected before being released to the environment. UV-radiation can also be used to physically crack certain chemical compounds like halogenated carbohydrates, drug traces in water and the like.
The disinfection potential of ultraviolet radiation can also be used to disinfect ballast water, which is discharged from ships in order to prevent foreign species from entering local water bodies in ports and rivers.
Such UV radiator units most commonly comprise and elongated gas discharge lamp with an essentially cylindrical lamp body, which is made from a quartz tube. At both ends, the lamp body is sealed and carries electrodes. The inside of the lamp is filled with a gas, which contains a small amount of mercury. Between the electrodes, there is a volume, in which the gas discharge develops such that the mercury is exited and emits ultraviolet radiation of the desired wavelength, the so-called germicidal wavelength.
These lamps need to be protected from direct contact with the surrounding water, mainly because of the operating temperature, which shall be maintained in a certain temperature interval for an efficient UV output, but also because of the potential contamination of the surface with non-transparent material, which reduces the UV output of the lamp. Finally, the lamp itself should be protected from mechanical damage. To this end, a sleeve tube, which is also manufactured from UV-transparent quartz material, surrounds the UV-lamp and prevents the lamp from coming into contact with the fluid to be treated.
The position of the lamp inside the sleeve tube has some effect on the operating conditions. In the case of cold water surrounding the sleeve tube, it is helpful to position the lamp in the centre of the sleeve tube, i.e. concentrically, so that no area of the lamp comes into close proximity of the sleeve tube, because such proximity could lead to cooling of the lamp in that area and ends to a reduction of the mercury vapour pressure inside the lamp. This could reduce the UV-output.
In the case of mechanical stress, mainly arising from vibrations or shock events, there must also be some protection to prevent the lamp from hitting the sleeve tube, which might result in the breakage of the sleeve tube, the lamp, or both.
Such operating conditions, which lead to mechanical stress events, arise if the ultraviolet lamp unit is used in portable devices or in mobile devices, like containers for use disaster areas for mobile disinfection or decontamination use, or in ships during the discharge of ballast water, because there may be vibrating pumps and tubes which impose vibration to the lamp units, and because of the high velocity of the water flow itself.
One example of an ultraviolet lamp, which is centred inside a sleeve tube by centering or damping rings, is known from U.S. Pat. No. 5,166,527, which is considered the closest prior art. In this document, centering rings preferably of a synthetic plastic material are located on the arc tube, which is the lamp body. The rings co-axially surround the tube and frictionally engage and support the tube, and assist in centering the tube within the sleeve.
While this arrangement is useful for centering the lamp inside the sleeve, is has been found that rings of plastic material, of rubber or similar devices are not sufficient to protect the lamp from mechanical damage, especially in mobile applications.